This invention relates generally to an imaging member including an electrically conductive grounding layer, and more specifically to an electrostatographic imaging member having an electrically conductive grounding layer comprised of alkyl acrylamidoglycolate alkyl ether polymer.
Photosensitive members having at least two electrically operative layers as disclosed in, for example, U.S. Pat. No. 4,265,990 provide excellent images when charged with a uniform negative electrostatic charge, exposed to a light image and thereafter developed with finely developed electroscopic marking particles. Generally, where the two electrically operative layers are positioned on an electrically conductive layer with the photoconductive layer sandwiched between a contiguous charge transport layer and the conductive layer, the outer surface of the charge transport layer is normally charged with a uniform electrostatic charge and the conductive layer is utilized as an electrode. In flexible electrophotographic imaging members, the electrode is normally a thin conductive coating supported on a thermoplastic resin web. Obviously, the conductive layer may also function as an electrode when the charge transport layer is sandwiched between the conductive layer and a photoconductive layer which is capable of photogenerating electrons and injecting the photogenerated electrons into the charge transport layer. The charge transport layer in this embodiment, of course, must be capable of supporting the injection of photogenerated electrons from the photoconductive layer and transporting the electrons through the charge transport layer.
Other electrostatographic imaging devices utilizing an imaging layer overlying a conductive layer include electrographic devices. For flexible electrographic imaging members, the conductive layer is normally sandwiched between a dielectric imaging layer and a supporting flexible substrate. Thus, flexible electrophotographic imaging members generally comprise a flexible recording substrate, a thin electrically conductive layer, and at least one photoconductive layer and electrographic imaging members generally comprise a conductive layer sandwiched between a dielectric imaging layer and a supporting flexible substrate. Both of these imaging members are species of electrostatographic imaging members.
In order to properly image an electrostatographic imaging member, the conductive layer must be brought into electrical contact with a source of fixed potential elsewhere in the imaging device. This electrical contact must be effective over many thousands of imaging cycles in automatic imaging devices. Since the conductive layer is frequently a thin vapor deposited metal, long life cannot be achieved with an ordinary electrical contact that rubs directly against the thin conductive layer. One approach to minimize the wear of the thin conductive layers is to use a grounding brush such as that described in U.S. Pat. No. 4,402,593. However, such an arrangement is generally not suitable for extended runs in copiers, duplicators and printers.
Still another approach to improving electrical contact between the thin conductive layer of flexible electrostatographic imaging members and a grounding means is the use of a relatively thick electrically conductive grounding strip layer in contact with the conductive layer and adjacent to one edge of the photoconductive or dielectric imaging layer. Generally the grounding strip layer comprises opaque conductive particles dispersed in a film forming binder. This approach to grounding the thin conductive layer increases the overall life of the imaging layer because it is more durable than the thin conductive layer. However, such a relatively thick grounding strip layer is still subject to erosion which contributes to the formation of undesirable "dirt" in high volume imaging devices. Erosion is particularly severe in electrographic imaging systems utilizing metallic grounding brushes or sliding metal contacts.
Also, in systems utilizing a timing light in combination with a timing aperture in the grounding strip layer for controlling various functions of imaging devices, the erosion of the grounding strip layer by devices such as stainless steel grounding brushes and sliding metal contacts is frequently so severe that the grounding strip layer is worn away and becomes transparent thereby allowing light to pass through the grounding strip layer and creating false timing signals which in turn can cause the imaging device to prematurely shut down. Moreover, the opaque conductive particles formed during erosion of the grounding strip layer tends to drift and settle on other components of the machine such as the lens system, corotron, other electrical components, and the like to adversely affect machine performance. For example, at a relative humidity of 85 percent, the grounding strip layer life can be as low as 100,000 to 150,000 cycles in high quality electrophotographic imaging members. Also, due to the rapid erosion of the grounding strip layer, the electrical conductivity of the grounding strip layer can decline to unacceptable levels during extended cycling.
Thus, the characteristics of flexible electrostatographic imaging members utilizing conventional grounding strip layer exhibit deficiencies which are undesirable in automatic, cyclic electrostatographic imaging systems.
The following patents illustrate conventional imaging members including features such as a layer comprised of alkyl acrylamidoglycolate alkyl ether polymer or a grounding strip layer: Yu, U.S. Pat. Nos. 5,096,795; Yuh et al., 5,063,125; Horgan et al., 4,664,995; Yuh et al., 5,063,128; Spiewak et al., 5,244,762; and Spiewak et al., 4,988,597, the disclosures of which are totally incorporated by reference.